PARIS -- Ethiopia's Tamirat Tola delivered a gritty run to claim gold with an Olympic-record time in a difficult men's marathon on Saturday, with two-time reigning champion Eluid Kipchoge bowing out of the race due to a back injury.

In a talent-packed field, Kipchoge was expected to battle to defend his title. Ethiopian marathon legend Haile Gebrselassie opened the race, but rather than welcoming Kipchoge at the line, he was there instead to congratulate his countryman Tola, whom he inspired to take up the sport as a 19-year-old.

"I am happy today because I fulfilled my goal," Tola said. "I prepared well. I trained hard so I could win. In my life, this is my great achievement."

Tola, 32, finished the race in 2:06:26, breaking the previous Olympic record set at Beijing 2008, made even more remarkable by the fact he only entered as a substitute two weeks ago after an injury to teammate Sisay Lemma.

"Sisay told me that it was better for him to drop out and for me to compete. He said, 'you can do better than me in my condition.' It is thanks to him, this victory also belongs to him for giving me this opportunity," Tola said.

Belgium's Bashir Abdi took silver and Kenya's Benson Kipruto took bronze.

Tola's dominant display saw him pull clear before the halfway mark and never let up.

His only previous Olympic medal was a bronze in the men's 10,000-metres at Rio 2016. It is also his second major marathon victory after winning last year's New York City marathon.

The marathon course began outside Paris' city hall, Hotel de Ville, and passed along sights such as Palais Garnier opera house, Place Vendome, the Louvre museum, the Trocadero and the Eiffel Tower and the Palace of Versailles. It ended with a scenic home straight in the shadow of the 17th-century hospital Esplanade des Invalides.

The footrace took on the air of the Tour de France at times, with multiple steep climbs amid a notably hilly course that was billed as one of the most difficult in Olympic history. The first climb took place around the 10-mile mark. A second hill a couple of miles later also had an impact, but it was the hill at the 18-mile mark that proved hardest, with a 13.5% incline at one point.

One of the notable runners who struggled was Kipchoge. He is one of the best marathon runners of all time, but he endured a tough race that even saw him almost a full minute behind the leaders at the halfway stage and reduced to walking up the hill at Mile 18.

He bowed out of the race soon after.

"Today was a tough day at the office. You can train for a very long time but one day, it can happen," Kipchoge said. "It's like boxing. You can go to a training camp for five months and be knocked out in two seconds. But life will continue.

"This is my worst marathon. I have never done a DNF. That's life. Like a boxer, I have been knocked down, I have won, I have come second, eighth, 10th, fifth -- now I did not finish. That's life."

Kipchoge added that the hills did not impact him, that it was the pain in his back after 12 miles that eventually forced him to stop.

When asked if this was his final marathon, Kipchoge said: "I don't want to comment on what will happen tomorrow. I want to try to evolve -- if I don't evolve, then I do other things.

"I don't know what my future will hold. I will think about it over the next three months. I still want to try to run some marathons."

It comes after one of the most difficult years of Kipchoge's career after he suffered significant online abuse following the death of his compatriot Kelvin Kiptum. Kipchoge suffered sleepless nights for some time after, resulting in him finishing in 10th at the Tokyo marathon in March -- his worst-ever result as a professional.